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Single frequency interference

What to do when several channels are missing, but they are all on the same 'multiplex'

What to do when several channels are missing, but they are all
published on UK Free TV

There are several different type of interference that cause problems. This page deals with the situation where:

There are two main causes of this type of intermitted interference: The current Freeview mulitplexes are shown in this diagram. If all of your missing channels are on a single row, you have "single frequency interference":



Local analogue interference

Local analogue interference is caused by household video devices that you can attach to a television such as:
  • Sky Digibox;
  • Video cassette recorder (VCR);
  • Personal digital video recorder (PVR);
  • Games console;
If you have any of these devices, you will need to work out which of these is blocking the reception of a Freeview multiplex by turning off the suspect device and then rescanning for channels on the Freeview box.

If powering off the device restores the Freeview channels from the blocked multiplex, you will need to either stop using the problem device's RF output by disconnecting the RF output cable permanently, or by changing the RF channel number that that device uses. See, for example, How do I change the RF output channel on a Sky Digibox?

You can find a list of the frequencies that are not in use at your location by putting your postcode into the My Freeview reception and looking under the "Free RF channels" section.

Non-wideband aerial in some areas

In some places you will need a wideband aerial to receive all the Freeview multiplexes. For example in Central Birmingham, the Sutton Coldfield has multiplex D on an 'out of group', so you cannot view Film4 or ITV2+1 without an aerial upgrade.

To find out if you need an aerial upgrade, see My Freeview reception.

Help with Freeview, aerials?
How do I get a test card with Freeview1
I would like to know if it is possible to receive UK terrestrial Freeview servic2
I have been told I would receive too much singal from my Freeview tansmitter as 3
Can my Freeview box receive more than one BBC and ITV region?4
Is it true that my 87 year old mother is entitled to a FREE upgrade when the ana5
In this section
Official aerial installers guide to the TV spectrum future1
Which free digital TV system will give me the most reliable reception?2
High pressure causing channel loss through "Inversion"3
Digital Region Overlap4
Freeview reception has changed?5
Two frequency interference 6

Comments
Monday, 10 January 2011
Briantist
sentiment_very_satisfiedOwner

6:47 AM

Rachel: I would still check your cables and connectors, they could easily have been damaged without your knowledge.

The interference can be almost anywhere in the reception chain, from the aerial to the TV.

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Briantist's 38,915 posts GB flag
Friday, 14 January 2011
P
Phil A
9:51 PM
Leominster

Any idea why I would suddenly experience single frequency interference when nothing on my set-up has been changed for well over a year? We can still receive Mux B on the system downstairs but not on the (old) kit upstairs for the last few days. This uses a Sony VTX-D800U stb (which I see from other sites has had issues in the past but mine has been glitch-free to date). Tried the factory resets etc quite a few times without success - in fact the resets don't seem to work at all 'cos afterwards, all the stations are still tuned. Post code is HR6 9HB and our transmitter is Ridge Hill.

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Phil A's 2 posts GB flag
Phil's: mapP's Freeview map terrainP's terrain plot wavesP's frequency data P's Freeview Detailed Coverage
Sunday, 16 January 2011
S
Spearo
9:25 PM

Hi - I have recently (end of November) bought a Hitachi HDR325. I live about 5/6 miles from the Wenvoe transmitter in South Wales. I have occasional single frquency interference on the COM4 (SDN) Multiplex so channels such as ITV3, E4, Fiver, Five USA receive no audio/visual (sometimes no visual but audio is ok/jumping). Nothing other than this box and a DVD player are connected to the TV. Aerial is new (mid last year). I can regain the full audio/visual is I "wiggle" the aerial connecter at the connection to the freeview box. Freeview on another TV in the house from same aerial is fine for all channels. Is this a faulty box or could there be any other possible cause?

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Spearo's 3 posts GB flag
Monday, 17 January 2011
Briantist
sentiment_very_satisfiedOwner

8:17 AM

Spearo: It is either a box fault, or it could be the "fly lead" connecting to the box.

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Briantist's 38,915 posts GB flag
Briantist
sentiment_very_satisfiedOwner

9:04 AM

Phil A: A factory reset won't change your reception, please check the things listed above.

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Briantist's 38,915 posts GB flag
Thursday, 20 January 2011
P
Phil A
10:38 PM

Briantist - sorry, red face here.... I now realise that I needed to rescan once I had disconnected the recorder from the tv, not with it still in the system. It was the recorder - can now receive Mux B after a rescan and reconnecting the recorder. Thanks for your help (and sorry!)

I'm curious tho' - why would this happen in the first place?

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Phil A's 2 posts GB flag
Friday, 21 January 2011
Briantist
sentiment_very_satisfiedOwner

7:35 AM

Phil A: I'm glad to hear that you have got your multiplex B back.

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Briantist's 38,915 posts GB flag
Monday, 24 January 2011
O
oyster
11:50 AM

My mother is a block of flats in Kensington W London has a new Sony Bravia working fine for 6 months. Last week just the ITV channels in row 2 above started to get blocky or not available. There is no other equipment in her flat (but other flats could have on shared aerial?) Any ideas please. Mains filter? Professional aerial check?

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oyster's 3 posts GG flag
H
Helen
7:10 PM

Hi - I am the proud owner of a brand new tv and HD box. I live in Lichfield, can get analogue Ch5 but no HD. I can live with that. However, yesterday (Sunday 23/1/11) no1 multiplex disapeared along with CBBC and a n other that I cannot find. CBeebies is still there.

I have read through the advice. There is nothing other than the HD box plugged ie no games and dvd and nothing near that might interfere with the signal. I have unplugged everything and plugged it all back in. I can get film 4 and ITV + 1

The aerial is in the loft, but it has worked for a week. Plus I live on one of the highest points in Lichfield so I don't think there is anything between me and the transmitter (the Lichfield one I think)

Any suggestions would be appreciated

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Helen's 3 posts GB flag
H
Helen
8:14 PM

I appear to be on here twice - sorry about that don't know what happened.

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Helen's 3 posts GB flag
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